1. Field of the Invention
The present invention relates generally to a position measuring apparatus, and more particularly, to a position measuring apparatus for realizing a high touch resolution and a driving method thereof.
2. Description of the Related Art
In general, a tablet Personal Computer (PC) or a portable terminal such as a navigator, a Personal Digital Assistant (PDA), a Moving Picture Experts Group Audio Layer-3 (MP3) player, a Portable Multimedia Player (PMP), or an e-book reader is equipped with a touch panel. Touch panels in such devices include resistive touch panels, capacitive touch screens, ultrasonic touch panels, and infrared touch panels, for example. Among these types of touch panels, the resistive touch panel and the capacity touch panel are popular. Resistive touch panels have decreased light transmission through a display compared to other types of touch panels, due to reflection from an air gap between Indium Tin Oxide (ITO) layers within the resistive touch panels. Resistive touch panels also cause an increased fatigue of a user's eyes compared to other types of touch panels, due reflection of outside light from the surface of resistive touch panels.
Compared to the resistive touch panel, the capacitive touch panel provides excellent durability and light transmission, and therefore, use of capacitive touch panels has recently become widespread. Conventional technologies regarding capacitive touch panels are included in Korean Patent Application Publication No. 10-1999-0064226 (published on Jul. 26, 1999), International Application No. PCT/US1996/17862, and Korean Patent Application Publication No. 10-2009-0048770 (published on May 15, 2009).
FIG. 1 is a simplified diagram illustrating a structure of a conventional position measuring apparatus.
Referring to FIG. 1, a touch panel includes an electrode pattern 10 with equally spaced channels arranged in one direction on a substrate (not shown), a driving chip 13 for sensing a touched position when a channel 11 is touched, and connection electrodes 12 for connecting the channels 11 to the driving chip 13. The electrode pattern 10 is formed by depositing a transparent conductive material (not shown) having uniform resistive components (not shown), such as ITO, to a uniform thickness on a substrate by, for example, vapor deposition. The substrate is generally a transparent film or glass on which an electrode pattern formed of a material such as ITO can be deposited. The electrode pattern includes X-axis grid channels (X-grid channels) and Y-axis grid channels (Y-grid channels) so as to detect a two-dimensional touched position. The connection electrodes 12 are individually formed at both sides of the channels 11 in order to connect the channels 11 to the driving chip 13.
A user touches a keyboard or an icon displayed on a touch panel having the electrode pattern 10 in a terminal with the user's finger or a conductive pen capable of touching a small area, such as a stylus pen, for example. Specifically, when the user touches a screen displayed on a display panel with the finger or the conductive pen, a variation occurs to the capacitance of X-grid and Y-grid channels arranged at the touched position. The capacitance variation is applied to the driving chip 13 via a connection electrode 12 at the touched position and the driving chip 13 detects position information, thus determining the touched position.
As illustrated in FIG. 1, for six channels 11, six connection electrodes 12 are provided. To increase a touch resolution of the touch panel of FIG. 1, the number of channels 11 must be increased. However, the increased number of channels 11 in turn increases the number of connection electrodes 12 that connect the channels 11 to the driving chip 13. As a result, the connection electrodes 12 occupy more space. The connection electrodes 12 are arranged at both sides of the channels 11 to prevent interference with a display area. As the connection electrodes 12 are arranged over a larger area, the peripheral area of the display screen is widened.
FIG. 2 is a simplified diagram illustrating another conventional position measuring apparatus in which a number of sensing electrodes is doubled in order to double a touch resolution in comparison to the conventional position measuring apparatus illustrated in FIG. 1.
Referring to FIG. 2, if the number of channels 11 of the touch panel of FIG. 1 is increased to 12 in order to double a touch resolution, the number of connection electrodes 12 of the touch panel of FIG. 1 is also increased to 12. Consequently, in the touch panel of FIG. 2, additional space for the additional connection electrodes 12 is required, thereby increasing the total installation space of all of the connection electrodes 12. The edges of the touch panel must also be widened by an amount corresponding to the installation space of the added connection electrodes 12. The increased width of the edges of a touch panel reduces the favorable aesthetics of a portable terminal having the touch panel according to FIG. 2 in comparison to aesthetics of a terminal having a touch panel according to FIG. 1.
In addition, the increased the number of connection electrodes 12 in FIG. 2 also corresponds to an increased size of the driving chip 13 that controls the connection electrodes 12, which is unfavorable in terms of installation space and fabrication cost.